1. Field of the Invention
This invention relates to value-bearing documents, and more particularly, to value-bearing documents, such as for example, bank notes, cheques, traveler""s cheques, share certificates, credit cards and identity cards.
2. Description of the Prior Art
Particularly having regard to the options afforded by modern color copiers and other reproducing systems, there is an urgent need for value-bearing documents to be provided with special security elements which make it difficult to produce a forgery using items of equipment of that kind. A large number of possible procedures have already been proposed for that purpose.
It is known for example for value-bearing documents such as value-bearing papers, cards, identity cards etc to be provided with security elements in the form of reflecting surfaces. Those reflecting surfaces are normally reproduced by a color copier as black surfaces. In this case however there is the possibility of subsequently applying a suitable, metallically shiny layer.
A further improvement in affording a safeguard against forgery is achieved when security elements in the form of structures which have an optical-diffraction or optical-refraction effect, so-called diffraction structures, for example holograms, so-called pixelgrams etc are used. However those security elements are comparatively expensive in terms of production.
It is also already known for security elements for value-bearing documents to be so designed that they are suitable in particular for viewing in a transillummination mode. For example AU-patent specification No 488 652 describes security documents which comprise a plurality of interconnected plastic webs, wherein at least one optically variable security element is arranged between those webs and a transparent window is provided in at least one of the cover webs in the region of the security element so that the security element can be viewed through the window. For applying the security elements, in accordance with the state of the art for example the procedure is such that an opening is produced in a plastic web which is disposed in the interior of the document, the security element being fitted into the opening. The security element is then fixed in the opening by cover foils which are applied at both sides. A procedure of that kind suffers on the one hand from the disadvantage that the operation of applying the security element gives rise to major difficulties and in particular the procedure requires lamination over the full surface areas of coaratively large regions of plastic foils. Inclusion of the security element between the two foils frequently results in a marked impairment in the level of brilliance and thus an adverse effect on the discernibility of the security element, in particular under poor lighting conditions. The known document can only be used with difficulty as a value-bearing paper, in particular banknotes, because it is fundamentally different in terms of its surface nature and other properties, from the properties of paper which are known and familiar in particular in the case of banknotes.
It is also already known from Australian banknotes for printing to be applied to the surface of transparent carriers in such a way that a given region is left window-like, that is to say transparent. In this case also however the advantages of paper have to be foregone. It is for example not possible to apply a watermark. In addition the tactile properties which are known to the citizen are different in comparison with paper (absence of the particular grippy feel). The tried and tested processing and treatment properties as well as the circulation properties of paper are also no longer enjoyed. Finally it is not possible in a pure printing process to produce specific security elements, for example diffraction structures.
It is also already known to use security threads as security elements in value-bearing documents, the arrangement being such that the thread or a corresponding strip is superficially exposed in a region-wise manner in order to be able to check additional security features which are preferably based on optical effects, on the thread or strip, for example printing patterns, diffraction structures etc. European patent specification No 0 229 645 describes the production of a security paper with an incorporated security element in the form of a thread or strip in such a way that two separate layers or plies of paper are formed, the layers of paper having regions of smaller thickness or openings therethrough. The two layers of paper are brought together and, during the operation of bringing them together, the strip which serves as the security element is introduced. In that respect the arrangement may also be such that the openings through the two layers of paper (on the top and underside respectively of the strip serving as the security element) coincide in aligned relationship so that the security element is exposed at the same location on the paper web on both sides thereof in order also to permit the security element to be viewed in the transillumination mode. In practice however it has been found that it was hitherto not possible to produce corresponding documents. In general terms on the contrary the arrangement was only so selected that the security thread or the security element was exposed alternately on the top side and the underside respectively. At any event a serious disadvantage of the known procedure is that, as the security threads have to be incorporated into the paper web, they may only be of comparatively small width in order not to destroy the cohesion of the paper in itself. In order however for the security threads to be of adequate strength in spite of their small width, it is necessary to use security threads of correspondingly large thickness, which can result in undesirable increases in the thickness of the value-bearing papers produced from the corresponding paper web; in that case, when the value-bearing papers are stackedxe2x80x94in spite of using the so-called wobble or offset procedurexe2x80x94those thickened portions would always be disposed in a relatively narrow region, which results in the sheets not lying properly flat and gives rise to problems in processing of the document.
The object of the present invention is therefore that of proposing a value-bearing document with a window-like security element suitable for transillumination, which can be produced easily and without adversely affecting the discernibility of the security element, while the problems known in regard to the production of security papers with incorporated security thread are not to be expected in the production procedure. The invention however seeks to ensure that forgery of the security element by pure printing or color copying is impossible, but at the same time there is a large number of different possible design configurations for the security element.
In accordance with the invention, in a value-bearing document having at least one security element and at least one window-like through opening which is closed by means of a light-transmitting film, to attain that object, it is proposed that the opening is subsequently produced in the finished carrier and the finished carrier thereafter serves for production of the value-bearing document such as a bank note, check form or the like and is closed by means of an at least region-wise transparent cover foil which projects beyond the opening on all sides and which is fixed on a surface of the carrier over the full area thereof.
In accordance with the invention therefore the attempt is no longer made to incorporate a security element into the carrier. On the contrary the opening is deliberately subsequently produced in the carrier and then the opening is closed again by means of a cover foil which is transparent at least in a region-wise manner, wherein the fact that the cover foil is fixed on the surface of the carrier, over the full area thereof, means that detachment of the cover foil which possibly carries a security feature which is based for example on optical effects is practically impossible, without damaging the carrier. By virtue of the arrangement in accordance with the invention it is readily possible to use a cover foil of comparatively large length or width, which means that it is possible to operate with cover foils of small thickness. At the same time a procedure in accordance with the invention also affords the possibility of providing windows of relatively large dimensions, whereas only very small dimensions could be achieved with the known windows which were produced during the paper production process. As the windows can be large, even when there are additional security elements it is readily possible for a sufficiently large region of the cover foil to be kept completely transparent. In this case, when a copy is produced using a photocopier or any other reproduction apparatus, the background will be visible in the region of the window so that the color of the background appears at that point in the reproduction. In that way forgeries can generally be easily detected. Furthermore, the authenticity of the value-bearing document can also be easily detected by the user as the presence or absence of a transparent region in the value-bearing document can be readily detected even with the naked eye. The fact that the opening in the carrier is covered over by means of the cover foil affords on the one hand the advantage that the stability of the value-bearing document does not suffer, in spite of the presence of one or even more through openings.
On the other hand the use of a cover foil affords further possible configurations in regard to the security element. Variations in the security element are further possible by virtue of different shapes for the window-like opening or a variation in the positioning of the opening or the provision of a plurality of openings which are possibly of different configurations.
In order to permit easy stacking of value-bearing documents, in particular value-bearing papers such as for example banknotes and in order also to make it substantially more difficult to pull off the cover foil and in particular as far as possible to prevent the cover foil from being unintentionally detached, the cover foil is desirably arranged in a depression in the carrier surface, which depression includes the window-like opening, while it is particularly advantageous for the carrier to be compressed to form the depression. The compression operation simultaneously smooths the surface of the carrier, which can be advantageous in regard to certain security features. For example, when security features are applied to paper by a hot stamping process, the optical efficiency thereof is reduced by the comparatively rough surface of the paper, and that can be avoided by suitable smoothing of the surface of the paper, which serves as the carrier.
In accordance with the invention the opening can be easily produced by means of a punching or cutting operation, in which respect mention is to be made here of the usual punching processes and in particular laser cutting as a cutting process.
It is basically possible for the depression and the opening to be produced in separate working operations. In order to avoid special adjustment operations and to achieve good alignment of the opening in relation to the depression, the procedure involved is desirably such that the opening is produced jointly with the depression in one working operation, and that can be effected for example by using suitable tools, for example special stamping and punching rollers.
The operation of producing the depression and applying the cover foil is simplified when the cover foil extends transversely over the entire width or length of the value-bearing document, that is to say there is a depression from one edge to another. More specifically, in such a case the procedure involved is desirably such that the cover foil is applied by means of pressure to the carrier of the value-bearing document with the depression being formed at the same time, the cover foil preferably being laminated on to the carrier in a rolling process.
When using a lamination operation for applying the cover foil to the value-bearing document, it is possible to achieve a particularly desirable method of manufacture. More specifically, in one run through a suitable machine, firstly the window-like opening and possibly also a plurality of openings can be formed, and thereupon the cover foil is applied by a lamination procedure in a further step.
For further improving the safeguards against forgery, it is provided in accordance with the invention that, at least on one side of the carrier, the cover foil and at least the adjoining surface region of the value-bearing document are overprinted with an interconnected pattern. With such a configuration, any manipulation on the cover foil is immediately visible because it is readily possible to provide printing in which just very slight displacements are clearly apparent.
In order to facilitate overprinting of the cover foil, desirably the cover foil may carry a bonding or primer layer at least on its free side which is not fixed to the value-bearing document or the carrier forming same.
Further possible ways of improving the degree of safeguard against forgery of a value-bearing document are afforded if, in accordance with the invention, the cover foil is a lamination foil comprising a transparent carrier film and a decorative layer which adheres fixedly thereto, wherein the decorative layer which preferably includes at least one lacquer layer is also transparent at least in a portion of the opening. The decorative layer can be of specific graphic configurations using different per se known processes in order thereby to afford additional recognition options for an original value-bearing document. It is always important however for the decorative layer to be at least partially transparent in the region of the opening.
It may further be desirable for the cover foil to be provided with at least one particular security feature which is based preferably on optical effects, and for at least a portion of the surface region of the opening to be left transparent, while advantageously at least one security feature is formed by a thin-layer arrangement and/or diffraction structure having an optical diffraction and/or refraction effect. Besides such diffraction structures or thin-layer arrangements as the security feature, the cover foil may also include for example reflecting surfaces, special prints, for example in the form of microscript etc. In that respect it is desirable if at least one of the security features is arranged in the surface region of the opening because that may then involve for example such a security feature which can be checked in respect of authenticity only in the transillumination mode, it being precisely transillumination processes that afford advantages when using automatic testing equipment.
When using a lamination foil as the cover foil, having a decorative layer and at least one diffraction structure as the security feature, the decorative layer is desirably such that it hasxe2x80x94starting from the carrier filmxe2x80x94a base lacquer layer which is provided at least in a region-wise manner at its surface remote from the carrier film with the diffraction structure serving as the security feature, at least in the a region of the diffraction structure a reflecting layer, and at least in the region of the opening a transparent protective lacquer layer. In that respect the structure of the decorative layer in the lamination foil in accordance with the invention is in principle the same as the decorative layer structure which is known per se from hot stamping foils for security purposes with a diffraction structure, and as is to be found for example in EP 0 559 069 A1. In addition, for applying the various lacquer layers, for introducing the diffraction structure and for producing the metallization which is possibly only partial, it is also possible to use the processes which are known in principle in connection with the production of hot stamping foils, and for that reason those processes will not be discussed in greater detail here. It will be appreciated that it would also be possible for a diffraction structure to be introduced directly into the carrier foil, that is to say, it would be possible to omit a separate base lacquer layer if a suitable carrier foil is used.
If, as the invention further provides, the cover foil is fixed on the carrier in such a way that its decorative layer faces towards the surface of the carrier, that gives on the one hand the advantage that the surface of the cover foil, which carries the decorative layer, is arranged in a virtually recessed or depressed relationship and thus protected to a certain extent from mechanical loadings. Furthermore, under some circumstances, it is possible to omit a special adhesive layer for fixing the cover foil on the value-bearing document, namely when the decorative layer and more specifically at least the transparent protective lacquer layer thereof already has sufficiently adhesive properties.
A further possibility in accordance with the invention provides that the decorative layer carries a layer of a hardenable adhesive, on the side of the decorative layer which is opposite the carrier film, in which respect it is possible to use for example reaction adhesives which completely react and thus harden only when subjected to the effect of appropriate heat or radiation, for example IR- or UV-radiation. The use of adhesives of that kind has the advantage that detachment of the cover foil when the adhesive has hardened is impossible without damage to the value-bearing document itself.
Finally it may be advantageous if the carrier has an application of adhesive in the region which serves for fixing the cover foil, in which case it is sufficient under some circumstances to provide only that application of adhesive on the carrier, although it may also be desirable if, in spite of the application of adhesive on the carrier, the cover foil is additionally provided with a corresponding adhesive layer. If it is only the carrier that is provided with the application of adhesive, that gives the advantage that it is possible to avoid adhesive possibly being spread in the region of the opening.